PDFs are generally image-only files. However, you can add a sublayer of text to them so that you can perform searches and so that you can copy text from the PDF.

In Acrobat 6, go to: Document|Paper Capture|Start Capture. Paper Capture performs an Optical Character Recognition (""OCR") process on the PDF, meaning it "reads" the image characters looking for letters. After the PDF is OCR'd, Paper Capture puts the text in the image the image, allowing you to copy the text and search for text.

The paper capture feature is built into Acrobat 6.0. In Acrobat 5.0, you will need to install the paper capture plug-in. You can find it here.

Keep in mind, you need the full Adobe Acrobat Program....NOT just Adobe Reader.